BACKGROUND: Internalizing problems, such as depression and anxiety, are common among children and adolescents, contributing significantly to impairment in various domains of functioning, including academic, social, and family life. While pharmacologic and psychotherapeutic interventions are effective in reducing symptoms, it remains unclear whether these treatments have similar effects to improve functioning. Functional impairment in youth can have long-term consequences, including increased risks for mental health issues, physical health problems, and social difficulties. Despite its importance, functional improvement is often overlooked in mental health intervention research. This study aims to systematically review and meta-analyze interventions that target internalizing symptoms, and assess both symptom reduction and improvements in functioning as treatment outcomes.

METHODS: This systematic review and meta-analysis will follow the Preferred Reporting Items for Systematic Review and Meta-Analysis guidelines. A comprehensive search of electronic databases, including CINAHL, EMBASE, MEDLINE, and PsycINFO, will identify randomized controlled trials published between 2014 and 2024 that evaluate psychotherapeutic or pharmacologic treatments for depressive or anxiety symptoms in children and adolescents. Eligible studies will measure both symptom severity and functioning outcomes. Data will be extracted independently by two reviewers, and effect sizes will be calculated using standardized mean differences. Multilevel meta-analytic procedures will be employed to assess both mean differences and variability within studies. Moderator analyses will explore factors such as treatment type, internalizing disorder subtype, and sociodemographic factors. Risk of bias will be assessed using the Cochrane Risk of Bias 2 tool, and the Grading of Recommendations, Assessment, Development, and Evaluations framework will guide the synthesis of the evidence.

DISCUSSION: This review aims to provide a comprehensive understanding of the effectiveness of mental health interventions for youth with internalizing disorders, focusing on both reductions in symptom severity and improvements in functioning. The findings will contribute to the development of clinical guidelines and treatment recommendations, emphasizing the importance of addressing functional outcomes in addition to symptom reduction. The results will have implications for the design and evaluation of future interventions aimed at improving the well-being of children and adolescents.